What is the normal range for PaO2 in adults?

• A. 60-70 mm Hg
• B. 70-90 mm Hg
• C. 85-95 mm Hg
• D. 80-100 mm Hg

Answer: (D)

PaO2 measures the amount of oxygen dissolved in arterial blood and is a key indicator of how well oxygen is moving from the lungs into the blood. In a healthy adult breathing room air at sea level, the normal range is about 80 to 100 mm Hg. This range shows adequate oxygenation and supports tissue oxygen delivery. Values below 80 mm Hg indicate reduced oxygen in the blood and potential problems with oxygenation, while values above 100 mm Hg can occur with supplemental oxygen but are not part of the typical resting reference range. That makes 80–100 mm Hg the best answer for the normal adult range.